Application of linear scale grating sensors！

Application of linear scale grating sensors
Application of geodynamics
Geodynamics in the field of earthquake detection, the principle and risk assess and predict phenomena such as sudden changes in the surface is very complex, and the stress and temperature changes volcanic area is by far could reveal volcanic activity and its key the most effective means of evolution of the scope of activities of the heart. Fiber Bragg Grating Sensor in this area mainly in rock deformation, as well as the detection of vertical seismic detectors and optical topography using seismometers and other aspects. Strain active zone typically contain both static and dynamic, static strain (including static deformation produced by the volcano) are generally located in the distance from the source close to the geological deformation, and to the source of the shock wave as a representative of the dynamic strain is possible in and the source of the Earth's distant surroundings detected. In order to get a fairly accurate source or volcanic source location to better describe the geometry of the source region and evolution, it is necessary to use a dense array of stress - strain gauge. FBG sensors are able to achieve long-distance and dense arrangement of multiplexed sensing broadband, high network sensor, in line with seismic testing and other requirements, so it certainly has great potential use in the field of geodynamics. It reported that, FBG sensors have been successfully tested frequency 0.1Hz ~ 2Hz, size 10-9 e rock and surface dynamic strain.
Application of Spacecraft and Ships
Advanced composite material fatigue, corrosion resistance is better, and can reduce the weight of the hull or spacecraft, for fast shipping or flying is important, so that the composite materials are increasingly being used in the manufacture of aviation navigation tools (such as aircraft wing).
To fully measure the condition of the hull, need to understand the different parts of the deformation moment, shear stress, deck suffered attack force, ordinary hull takes about 100 sensors, so the wavelength multiplexing capability strong FBG sensors best suited to the hull testing. FBG sensing system to measure the bending stress of the hull, deck and measurable waves wet attack force. An interference detection performance of the fiber grating 16 multiplexing system successfully achieved within a bandwidth of 5kHz range resolution of less than 10ne / (Hz) 1/2 dynamic strain measurement.
In addition, in order to monitor an aircraft strain, temperature, vibration, landing operating state, the ultrasonic field and acceleration will usually require more than 100 sensors, so the weight sensors to be as light as possible, the size as small as possible, so the most dexterous FBG sensors It is the best choice. In addition, there are actually a composite material aircraft strain in both directions, the material embedded FBG sensors are ideal intelligent multi-element multi-axial strain and temperature measurement.
Application of civil engineering structures
Monitoring of civil engineering structures are FBG sensors the most active areas. For bridges, mines, tunnels, dams, buildings, etc., the above-mentioned structure by measuring strain distribution, can predict the structure and condition of partial load, easy maintenance and condition monitoring. FBG sensors can be attached to the surface of the structure or pre-embedded structure, the structure at the same time impact detection, shape detection, control and vibration damping, but also to monitor the structural defects of the situation. In addition, a plurality of FBG sensors can be cascaded into a sensor network, the structure of quasi-distributed detection, and sensor signal through the computer for remote control.
One of the building structure FBG sensors can detect for the bridge. The application, a set of fiber grating is adhered to the surface of the bridge composite bar or on the surface of the beam to open a small groove, so that the bare core portion embedded grating groove (easy protection). If you need more complete protection, it is best at the time of the construction of the bridge grating buried composite bar. At the same time, in order to correct the temperature effect caused by the strain, stress and temperature can be used to separate the sensor arm, and the two arms are installed in each beam.
Two linear scale gratings having the same center wavelength instead of Fabry - Perot interferometer mirrors *, to form a full Fabry - Perot interferometer * (FFPI), so that the use of low coherence interferometry phase noise minimized, which one way to achieve a high dynamic strain measurement sensitivity. FFPI combined with the other two FBG, wherein a grating is used to measure strain, and the other is protected (from stress), to measure the temperature and correction effect, while achieving a measurement of three quantities: temperature, static strain, instantaneous dynamic strain. This method combines the advantages of coherence interferometer fiber Bragg grating sensors and, in 5me measurement range to achieve less than 1me static strain measurement accuracy, temperature sensitivity, and less than 0.1 ℃ 1ne / (Hz) 1/2 dynamic strain sensitivity.
Application of the Electric Power Industry
FBG sensors are not subject to electromagnetic interference and achieve low-loss transmission over long distances, making it an ideal choice for the power industry applications. Wire load, transformer winding temperature, high current, etc. can use FBG sensors linear scalemeasure.
In the power industry, the current converter can change the current into a voltage changes, voltage change could piezoelectric ceramic (PZT) is deformed, and the use of fiber grating affixed to the PZT on the wavelength shift, it is easy to know its deformation, Further sensed current intensity. This is a relatively inexpensive method and does not require complex electrical isolation. In addition, the excessive pressure exerted on the wires may cause dangerous snow and other events, so line inspection wire pressure is very important, especially for those not easily detected mountainous wire. FBG sensors can measure the wire load, the principle of the change of load changes into the stress of a metal plate close to the wire, the stress can be adhered to a metal plate FBG sensors to detect . This is the use of FBG sensors to achieve long-range under harsh environmental measurements instance, in this case, the next larger pitch of the grating, so without fast modulation and demodulation.
Applications in Medicine
Medical sensors are mostly used in electronic linear scalesensors, it is not suitable for many medical procedures, especially in the treatment of microwave hyperthermia (radiation) frequency, ultrasonic or laser radiation in the field. Since the electronic sensors are metallic conductors interference current, voltage, etc. susceptible to electromagnetic fields caused by the sensor head or thermal effects around the tumor, causing incorrect readings. In recent years, the use of high-frequency current, laser and microwave hyperthermia surgery to replace more and more attention of the medical profession, and the small size of the sensor in medical applications is very important, because of the small size of human tissue less damage, while the smallest sensor FBG sensors precisely so far can do. It is possible to accurately measure the internal body tissue information local temperature, pressure, acoustic wavefield through Injury to minimum. So far, the FBG sensing system has been successfully tested an ultrasonic field temperature and diseased tissue, in the range of 30 ℃ ~ 60 ℃, access to a resolution of 0.1 ℃ and the accuracy of the measurement results of ± 0.2 ℃, the measurement resolution ultrasound is 10-3atm / Hz1 / 2, which provides useful information for the study of diseased tissue.
FBG sensors can also be used to measure the efficiency of the heart. In this method, the doctor embedded with fiber Bragg grating thermodilution catheter inserted into the patient's heart in the right atrium, and injected a cold solution of people, the pulmonary artery to measure blood temperature, combined with pulse power output of blood can know the heart, this cardiac monitoring is very important.
In Chemical Sensing
FBG linear scale sensors can be used for chemical sensing, because the center wavelength of the grating with a refractive index changes, and loss of concentration changes between raster prosperous wave interaction and the environment of chemicals will cause changes in the refractive index.
Long period grating (long period fiber grating, LPFG) and fiber Bragg gratings, as is formed to produce a periodic modulation of the refractive index of the optical fiber axis, the cycle is generally greater than 100μm. Its coupling mechanism is: Forward transmission core mode is coupled into the cladding modes forward several specific wavelength transmission, cladding mode quickly lost, so LPFG essentially no backward reflection, in its transmission there are several absorption spectrum of a specific wavelength. LPFG changes in the refractive index of the fiber cladding material is more sensitive than that of the fiber Bragg grating, any change in the refractive index of the cladding material will change the characteristics of the transmission spectrum, an absorption peak changes, so long-period grating refractive index measurement system resolution 10-7 sensitivity can be achieved. Now with a long-period grating measured the concentrations of many chemicals, including sucrose, ethanol, hexanol, hexadecane, CaCl2, NaCl, etc. In principle, any absorption spectrum and having a refractive index between 1.3 and 1.45 chemicals are available to detect long-period grating.

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